


The Safeword is "Gwen"

by Nostradumbass (singularthey)



Category: Merlin (TV)
Genre: Age Play, Alternate Universe - Modern Setting, Barebacking, Chastity Device, Daddy Kink, Diapers, Dirty Talk, Fantasizing, Incest Play, Infidelity, Lack of Communication, M/M, Plot What Plot/Porn Without Plot, Rimming, Scat, Sex Toys, Sexual Roleplay, Watersports
Language: English
Status: Completed
Published: 2014-03-13
Updated: 2014-03-13
Packaged: 2018-01-15 14:39:40
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 6,848
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1308520
Author URL: https://archiveofourown.org/users/singularthey/pseuds/Nostradumbass
Summary: <blockquote class="userstuff">
              <p>Merlin only has Arthur for the day, and he is going to enjoy him to the fullest, in the filthiest way he can manage.</p>
            </blockquote>





	The Safeword is "Gwen"

**Author's Note:**

> Written for a [kinkme_merlin prompt](http://kinkme-merlin.livejournal.com/2936.html?thread=11243640#t11243640):
>
>> Give me the dirtiest, filthiest porn you can come up with. Watersports, scat, whatever. Run wild, writer!anon! All I ask is no non-con.
> 
>   
> There is a more complete list of warnings in the end notes; skip there if you have questions about the content before reading. 

Merlin woke to a weight on his bed, the sudden dip jolting his body to the left. His eyes shot open, and Arthur filled his field of vision, smirking down at him, beautiful as ever. He straddled Merlin's legs, settling his weight over Merlin's pyjama-clad thighs.

"To what do I owe the pleasure?" Merlin asked, his sleep-thickened tongue slurring the words.

"We need to get started on your punishment," Arthur answered simply, opening his fly.

Oh, that. Merlin thought it was a bit early but, well, he did like his punishments. Usually, anyway. He played along. "What am I being punished for?"

"Well, you've wet the bed, for starters."

Merlin's eyes went wide. He was sure he hadn't, he hadn't wet the bed since he was a _kid_. He pushed up to check, just in time to see that— _Oh_. Warmth spread around his cock and over his lower stomach as Arthur pissed on him, moving his cock so the stream went all over, soaking Merlin from navel to thigh. He groaned, enjoying the smell, the feel of liquid pleasure, Arthur's mark on him. He wondered absently if he should let go, add to the mess himself, but— no. No need to make the cleanup last any longer, or to cover up Arthur's scent on him. He could hold it for a bit longer, at least.

It was over much too quickly, Arthur wiping the last drops of piss off his cockhead with the still-dry knee of Merlin's pyjamas. Merlin lifted on hand to rub at his cock, cloth clinging heavily to it, and shuddered at the sensation.

"So I have." He peeled the wet material away from his skin, let it snap back into place. "What's the punishment, then?"

"We'll get to that in a bit," Arthur said, sliding off of him, careful to avoid getting his own clothes wet. "Right now, I'm going to clean your mess up. I've already run a bath — you get in, and I'll join you when I'm through."

Merlin grinned and pushed himself up slowly, stretching as he went. He did not regret giving Arthur his spare key at all.

X

The warm bath water was heavenly, and yet not quite relaxing. Merlin could hear Arthur moving through the flat, and he could only wonder what was in store for him. There was also the issue of his bladder, of course; he always needed a piss in the morning, and without actually letting go in bed, he found himself making a serious, conscious effort to not just let it leak out into his bath water. He wouldn't mind that exactly, but he and Arthur had so few chances to indulge in their shared fetish, he felt like he couldn't waste it. He had to wait.

Finally, Arthur returned from his task of cleaning Merlin's bed and clothes. He was undressing almost as soon as he entered the room, and unceremoniously dropped into the water with Merlin moments later. The tub was small, hardly enough for just once person, much less two people, but Merlin couldn't complain, enjoying having Arthur close in any way he could.

"So she's out of town?" he asked, once Arthur was settled in, relaxing against the opposite end of the bath.

"Visiting her parents." He grinned toothily, head back and eyes closed. "She said I should spend some time with my mates."

Merlin nearly laughed. He held his cock, stroking slowly and leaning back himself. "So you thought you'd just come over and piss in my bed?"

Arthur chuckled. "Merlin, don't blame your accidents on me. It only makes you look worse."

Merlin hummed, nodding slightly. "Yes, I did notice you came away dry."

At that, he pointed his cock up, the head of it poking out of the water, and squeezed down on his bladder, letting his piss stream up and directly at Arthur. He missed his intended target, landing inches short of Arthur's chin, but was able to paint Arthur's chest with urine while his older lover spluttered in false indignation before reaching for Merlin's cock, wrapping his hand around Merlin's own and pointing the stream back at him. Merlin laughed, clenching as he did so, only half-successfully; each laugh sent another spurt out towards his stomach, though he still had plenty left to give.

Arthur mock-glared at him, rising up and stepping out of the tub and grabbing a washcloth from beside the sink. "Can't even enjoy a bath without you making a mess, can I? I'll have to add on to your punishment, just for that."

Merlin let his cock fall back into the water, relaxing enough to let the rest of his bladder empty into the water, the area around his thighs turning a few degrees warmer. "Right. What punishment am I getting, again?"

"One befitting a _baby_ who can't keep from pissing all over," Arthur said, wiping his chest off. Merlin watched as he finished up, then reached down below the sink for a bag he hadn't noticed before. He watched in anticipation as Arthur rooted around in it, then came up with something in each hand.

The nappy was exciting enough. They took some getting used to, but the feeling of just letting go, of holding it against the body, and not having to clean up after were all ideals for him. The cock cage, on the other hand? Not so much. He knew chastity devices always paid off in the end — Arthur never went the whole day without letting him get off, and the build-up made the experience once it was off fantastic, but he always felt disappointed when he remembered that he couldn't get off every time Arthur did something arousing — which was all the time, really.

Of course, if he was really against it, they did have a safeword. They'd never used it, except in one circumstance when Arthur's wife returned from a short holiday early. The moment her name was uttered, their fun ended, and Arthur went back to being a supposedly devoted, monogamous husband whose filthiest idea was spanking his equally devoted, monogamous bride.

Merlin would far rather endure the cock cage than even think about Arthur going back to her early, so he lifted himself from the tub, settling onto the nappy once it was laid out. Thinking about her had been effective in making him soft again, and Arthur had no trouble locking him into the cage, then wrapping him up. He added powder, more for the play than anything else, and helped him stand.

Merlin shifted from foot to foot, the material crinkling between his legs. It was a strange, but not unfamiliar sensation, and he wondered momentarily how long it would take before he could let go this time.

"How's it feel?" Arthur asked, walking around him to observe his handiwork.

"Fine. Like a nappy and a cock cage."

"Good," Arthur murmured, turned toward the toilet. He lowered the seat, sitting down on it in all his naked glory and beckoning Merlin forward. He pointed to the floor, and Merlin fell to his knees. "Now for the second part of your punishment."

He took hold of Merlin's jaw, opening his mouth with his thumb, and with his other hand fed his lover his cock. Merlin took it greedily, sucking even while he lifted questioning eyes to Arthur's face.

"You're going to take care of Daddy's cock while he takes a shit," Arthur instructed.

Merlin cringed slightly. Scat was not his favourite, although as long as it was clean and it made Arthur happy, he was willing to do it. He sucked and bobbed obediently, trying to ignore the smell, the splashing sounds from the toilet, and concentrate on the delicious, salty taste of Arthur's prick and precome, the sound of his moans and the way he chanted _yes_ over and over, with Merlin's name. He focused on the feeling of Arthur's hand on his face, occasionally petting his hair, sometimes settling on his cheek to feel his cock through Merlin's flesh.

Merlin knew by the way Arthur relaxed with a quiet grunt that he had finished, that Merlin was behind and liable to receive another punishment for being so slow. He didn't regret it, though; the feel of Arthur's cock on his tongue was one of the best in the world, and he relished the time it spent there enough to risk it. Still, he sped up, one hand coming up to grasp the base so his tongue could focus on the head, the other fondling his massive balls. Arthur's hand gripped his hair, and he knew he was close, giving one long, hard suck to the tip of his cock.

With a strangled noise, Arthur came, his ejaculate overflowing in Merlin's mouth. He would not let up on his hold, though, and so Merlin choked down what he could, the rest running down his chin and dripping onto the floor.

Arthur sighed deeply, and Merlin waited patiently to be let go. He counted thirty seconds, then looked up, imploring Arthur to remember that he was there and let him move.

Arthur caught his eye, and a second later Merlin felt another hot jet of liquid in his mouth. It wasn't much, barely a mouthful, but enough for Merlin to know it was piss and not come, to get the taste in his mouth and know Arthur had been waiting until he could get it out. He swallowed some reflexively, jumping up and spitting into the sink as soon as Arthur released his hold on his hair.

He loved piss, but he didn't really enjoy having it in his mouth. Oh, well — he wasn't really supposed to enjoy a punishment really, was he?

X

Eight hours. Eight hours Merlin had endured Arthur being ridiculously attractive, right across the table as they ate, then next to him on the sofa as they watched a (boring, tedious, not nearly as interesting as Arthur) football match, recorded from the evening before. Eight hours of wincing whenever he felt a little bit turned on. 

Either hours, another blowjob, one extremely long snog, and a long, drawn-out handjob.

Eight hours of an increasingly full bladder.

Arthur had made a point of keeping them both up in liquids; breakfast had included more juice and milk than toast or eggs, and the game had been accompanied by several bottles of beer. Three hours ago, Merlin had held up an empty glass bottle while Arthur pissed into it, pulling his cock out and aiming for him so that Arthur wouldn't miss a second of the game, even if it could be paused.

Their late lunch was almost torture. Arthur was enjoying his food far too thoroughly, for one thing, and Merlin could barely look at him, afraid he might catch him attempting to fellate his sandwich, or practically orgasming at the taste of beef. Meanwhile, he had the task of emptying an entire glass of water, which was incredibly intimidating when he could feel how distended his bladder was through his abdomen. He could barely touch his food, dreading the feeling of adding anything to his stomach.

Beneath him, his nappy was pitifully dry. He knew it was there, knew he could use it at any moment, but for some reason he couldn't break past the reflexive instinct to clench whenever he attempted to let go. He had had the same trouble before, especially the first few times Arthur had put him in a nappy, but he could only guess now that the reason was that it had been too long.

It always felt like it had been too long, of course.

He sipped carefully at his glass of water, trying to down it slowly enough that his throat and bladder might not even notice.

But Arthur did. "Merlin, why haven't you finished your meal?"

Merlin squirmed, unable to answer. He didn't need to, though; Arthur had him caught.

"Haven't you gone at all yet?" Arthur asked, a hint of worry in his voice. When Merlin shook his head, Arthur _tsk_ ed softly. "I'll bet it hurts to hold all that in, doesn't it?"

"A bit," Merlin answered, more or less truthfully.

"Hmmm." Arthur stood, taking Merlin's plate and unfinished food. He cleared the table of all but the glass of water, then pushed Merlin's chair back. "We're going to have you finish this glass, all right? Then I'll help you go. Can you do that?"

Merlin nodded, acting more sure than he felt. He tilted up his head as the glass came to his lips, his brow creasing as he concentrated just on swallowing, trying to ignore everything else.

The water seemed unending, like it was coming from a waterfall and filling him like a balloon. His throat was sore when it was finally empty, and Arthur moved to put it with the other dishes, then came back to Merlin, directing him to stand up and positioning him over the table. He put his hands down, but Arthur moved them out from under him, gently urging him down onto his stomach.

The wood was rough under his belly; he had worn nothing but the nappy since that morning, since, as Arthur said, babies didn't need to wear "ridiculous hoodies and skinny jeans." Arthur pushed him up until all his weight was on the table, only his toes still on the ground, and undid the nappy from the wrong side, pulling it back to see that it was, indeed, dry.

"Oh Merlin," Arthur murmured, stroking his arse. "Well, I know how to help you. Stay right there."

Merlin did as he was told, resting the side of his head on the tabletop. After a little over a minute, he heard Arthur return to the kitchen, felt his warm hand on his thigh, followed by a cold, slick finger at his hole. He gasped, surprised at the feeling, but it only made him clench up more. Arthur stroked his back as he pressed a finger in, probing around first with just the one, then two.

They both knew from Merlin's whimpers just when he found what he wanted. He paused, then pressed mercilessly as well as he could against Merlin's prostate. "Come on," he urged, repeating the action several times. All he earned was a whimper, though; it was too much, enough to increase the pressure on Merlin's bladder and torture his encaged cock all at once, but not the tipping point he needed.

Arthur sighed, pulling out his fingers.

"I guess I'll need to try something bigger then, won't I?"

Merlin pressed his forehead to the table, willing the tears to not come to his eyes. He was certain this would be torture; even if it helped him finally piss, arousal was almost inevitable, even though the pain of being opened up. He wasn't entirely sure the abuse to his cock was worth it.

Arthur pulled him back slightly, so his hips were just at the edge of the table. He fastened the nappy again, keeping it low, just over his thighs, and loose enough that he could get to Merlin's hole with ease. In no time at all he was slick and pressing into him, and Merlin concentrated on the pain of the stretch, rather than the satisfying sensation of being opened with Arthur warm, firm cock; condoms were, for them, a thing of the past. Merlin used them when he was with other men, and he only shared Arthur with his wife, so they had forgone the precaution in favour of feeling as much of one another as they could.

Merlin almost wished Arthur had used one, though. He was never hard once he was first entered, but the sensation of being full and the rough friction of Arthur's thrusts were the best aphrodisiacs. He was reduced to gasping sobs shortly, his cock straining painfully against its cage.

Then Arthur adjusted, pulling his hips up just slightly, and Merlin knew at least some relief as the pressure on his bladder from the inside became too much to bear. He cried out as he started to piss, and Arthur nearly dropped him in his haste to get a hand into his nappy, cupped around the head of his encaged cock and catching all the freshest urine he could, groaning and grinding up against Merlin's backside.

Merlin hardly noticed, lost in sweet relief. His nappy was absolutely saturated with piss, sagging heavily where it was not supported by the table. It splashed against Arthur's palm and back against his cock, getting the head wet and hot before leaking back down between his fingers, coming fast enough that it created a small pool before the material could absorb it.

As he finished, Merlin realised his face was wet, and hoped Arthur hadn't noticed.

His lover did seem distracted, pulling out and stripping his cock with his piss-drenched palm. He stayed close, near enough that he painted Merlin's backside white as he came, then smeared it into his skin with both hands, licking what he didn't spread off of him eagerly.

"Such a good boy," Merlin heard him mutter, and in spite of everything, it made him feel wonderful.

X

Four hours later, Merlin, back pressed to Arthur's chest as they watched a film from the sofa, set down his cup of tea and twisted around. "Arthur?"

Arthur looked at him, but didn't respond.

Merlin nearly rolled his eyes before recalling his part. "Daddy?"

"Yes, Merlin?"

"I'm pissing."

That caught Arthur's attention, and his hand immediately went to the front of Merlin's nappy, squeezing the front of it around his prick. Merlin moaned happily; shortly after the lunch incident, Arthur had added his own piss to the soaked material, then removed the cock cage. He hadn't been given the opportunity to get off yet, aside from a few erections he'd been advised not to handle himself, but he _could_ get hard, and better still, pissing came that much easier once he'd crossed the barrier of soaking himself once. He was able to thoroughly enjoy every squeeze and stroke, every burst of wet heat that hugged his very happy cock. The nappy was a wreck, barely able to contain the third load of piss, and it squelched in protest as Arthur shoved his hand in, jerking Merlin off roughly.

The pleasure as he reached the edge was intense; as he'd predicted, the pent-up sexual energy in him all gathered at once, like a dense ball of toe-curling arousal at the base of his cock. His balls drew up, and as soon as the last of the piss was out of him it was followed by hot come, coating the inside of his nappy and Arthur's hand, which his lover dragged up his stomach, resting on the lower part of his ribcage.

They sat in contented silence, the movie forgotten. Merlin could feel Arthur's cock poking at his back, but decided not to mention it until Arthur did, wanting to bask in the moment.

A thought came to him, unbidden, as he nestled against Arthur's chest, and before he could stop it it spilled from his lips. "Do you ever think about doing this with her?"

There was no question of whom he was speaking. Arthur didn't seem overly bothered by it, though. "Sometimes. Not often. It doesn't seem worth dwelling on; I'm certain she wouldn't do it. She doesn't even like me to have the door open, even just a little, when I piss at home."

Merlin felt a deep satisfaction in the knowledge that if nothing else, this would keep Arthur coming to him. He didn't doubt Arthur's love for him, or his attraction to him, but he was sure that if _she_ could satisfy this, he'd have a much harder time fighting Arthur's morals — and his own. "So you never thinking about just doing it? Maybe just pissing in her pussy after you fuck?"

"We don't ever _fuck_ , Merlin, watch your mouth. She and I make love." He sounded slightly regretful about that, too, and Merlin took more and more guilty pleasure from it.

"So you don't fantasise about doing that to any woman?" he asked, clearly fishing and not care that it was apparent.

"Well..."

Merlin looked up at him, a little startled. Although Arthur was unabashed about their own tryst, he was a bit surprised to find that Arthur thought of anyone else beyond the two of them. "Really? Who, then?"

Arthur's cheeked flushed ever so slightly, and Merlin's jealousy gave way to intense curiosity. His eyebrows rose, and he met Arthur's eyes, refusing to look away.

"Come on, tell me. I'm already the other woman, what do I care?" Well, of course he cared, but that was beside the point.

Arthur sighed deeply, looking away. "Morgana. I think about Morgana."

Merlin's jaw dropped. "But she's your sister!"

"Half," Arthur corrected automatically, getting redder. "But that's sort of the point. I don't even— It's not even about the sex so much. I really, really want to punish her for what she's done to our family, but I don't want to hurt her. It all comes back to pissing all over her, and inside her, and telling her no man would ever want her after, and— and I'm a bloody pervert."

Merlin kissed his cheek. "You're my pervert, though."

Arthur made a noise, pretending like it didn't matter, but Merlin could tell he was relieved his secret had been taken so well. "What about you? What kind of fantasies do you have?"

It was Merlin's turn to blush, though he didn't hesitate in telling. "Pretty much this, but with other people, too. I spend a lot of time thinking about going to the beach, and pissing myself while everyone around us is none the wiser. You could piss on me, too, if we were careful about not getting caught. I think it'd be easy enough, so long as we went in the water first and got wet. Probably nobody would even look at us twice."

"Mmm," Arthur agreed, apparently enjoying the idea himself.

"Or," Merlin went on, "staying here, but inviting some other guys over as well. And I'd just stay naked, or mostly, anyway, while you all watched football or something, and you'd use me when you needed a piss. And maybe you'd let everybody else use me, too, so nobody would have to get up. I'd be like your mobile urinal."

Arthur thrust up lazily against his back to show his approval of the idea, and Merlin pressed back into him.

"Mine aren't any more likely than yours, though. I mean, they may seem feasible, but it always comes back to the problem of getting found out. I can't think of any real way to ensure nobody would say anything to the wrong person, short of paying them, and I don't find that idea appealing. It's all moot if she finds out, isn't it?"

"We could go on holiday," Arthur said, sounding a little too hopeful. "Just you and me, in secret. We could go to another country, so nobody would know us or her, and do everything you want."

Merlin smiled wryly, trying not to believe him. It sounded like a wonderful idea, which meant it would only hurt more when they couldn't manage it. "And bring Morgana?"

Arthur's hips jerked involuntarily, and he gripped Merlin's hips. "Fuck."

Merlin turned in his arms, grinning wickedly. "You like that idea? You getting to punish your sister while I get used like a human toilet in public? You could chain us both to a post and put a sign up: 'on-the-go loos' or something, then sit by and watch men come up and piss in her hair and all over my cock. We wouldn't be able to do anything to stop them, even if we wanted. I know I wouldn't, so long as you made sure to stop by and make use of us."

Arthur thrust up, and Merlin took pity on him, undoing his fly and pulling out his stiff cock. He stroked it slowly as he went on, an idea catching him.

"And maybe your father would be there," he said cautiously, watching Arthur. An especially hard buck of his hips confirmed his suspicions. "He probably deserves some punishment himself, honestly, but he wouldn't get any, no. He's certainly like to punish Morgana and me, though. Piss right in her face for being so uncaring, then turn and soak mine, too. I know he never liked me much. He'd probably love showing me just how he felt. And for you, I'd love to be shown."

Arthur swallowed thickly, his eyes shut tight. It wasn't often Merlin had that sort of power over him, and he enjoyed drawing it out, playing with his foreskin and keeping his strokes light. He didn't really enjoy the idea of being pissed on by Uther Pendragon, but it was true that he'd like it well enough if it got Arthur off.

"And then after, he'd have you come over, and make sure you covered every inch of us he didn't, so we'd be wallowing in Pendragon piss. We'd have our hands bound, so when we'd need to go, we'd be helpless, and just have to piss all over ourselves, too. But maybe you, or even your father, would use me, hold my cock while I went and make sure I piss all over her instead, like she deserves. Then you'd get the pleasure of taking us home and cleaning us up — but not right away, no. First we'd have to just sit and stink, smell like the toilet behind a pub, and more importantly like your piss."

That hit the spot, apparently, and Arthur jerked up in his fist and came. Merlin hardly had time to keep it off his face, instead cupping his hand to catch most of it that way. He licked what he couldn't catch up, then sat back, letting what was in his hand drip onto his chest and down his stomach. He almost regretted coming earlier, wishing he could enjoy Arthur's arousal, too, but it was too soon.

And there were more pressing matters to attend to. With somewhat shaky legs, he started to rise, but Arthur grabbed his arm, stopping him.

"Where are you going?"

"To the toilet," Merlin said, jerking his thumb in its direction. "I've got to shit."

Arthur tugged on his arm, pulling him back down to the sofa. His bottom squelched wetly at he sat. "You're wearing a nappy, aren't you?"

Merlin made a face. "I'd rather not."

Arthur, astonishingly, could manage a perfect kicked puppy face very shortly after coming. "Come on, for me? You've teased me with all your talk, it's the least you could do for your Daddy now."

Merlin was conflicted. The idea was wholly unappealing to him, but he didn't want to use their safeword, and he did enjoy pleasing Arthur. Plus, after making the mess he already had, he was fairly sure letting go in that respect inside his nappy wouldn't be too hard. He sighed. "Oh, all right."

Arthur grinned from ear to ear, tugging on his arm again. "Here, sit on my lap first."

Merlin did, settling his soaked arse right across his thighs.

Arthur held his come-covered hand with his own wet one, squeezing their messy palms together. "Now go."

With some reluctance, Merlin took a deep breath and pushed. He screwed up his face in concentration, and with some effort, felt his success push out of him, hot and solid. Arthur grabbed at his bottom, groaning as he felt the evidence in his hand, obvious even though the nappy. Merlin knew his face was red, but he pressed on, emptying his bowels and trying to remember that it was making Arthur happy, trying to feel the relief of emptiness. It was still unpleasant, but he managed, and when he was done he sighed, trying not to move until he was sure he could get up without any leaks. His nappy had taken quite a lot of abuse, after all.

"Thank you," Arthur whispered, hugging him close. "You're so, so good. You're _wonderful_."

Merlin smiled, but tightly. "I'm glad you enjoyed it. Can I go change out of this now?"

"But I don't have any more nappies."

"Arthur, I'm not going to sit around in shit for the rest of the day. Not even babies put up with that."

Arthur pouted, but seemed to realise he was right. "Shall I run out to get nappies, then?"

"How about we just say your baby boy has graduated from nappies to— well, I have an old jock still. How about that?"

Arthur considered. "All right. But to prove you're a big boy, you can't take it off."

"All right."

"Not even to use the toilet."

"Okay." Merlin wasn't sure exactly how wetting himself would prove he was a "big boy" in their roleplay, but he supposed asking for it to be perfectly logical went out the window when his Daddy asked him to shit himself, anyway. "I'm going to change, now."

"Can I clean you up?" Arthur asked eagerly, following him as he rose.

"Only if you don't play with it," Merlin warned, and Arthur nodded, clearly pleased.

In the bathroom, Merlin was relieved to find he still had a pack of moist wipes from a previous day spent as Arthur's baby, and he handed them to Arthur, laying down on the floor with his hands resting on his stomach and focusing determinedly on the ceiling rather than his own filth. He shuddered at the coolness of the wipe, but managed to stay otherwise still until prompted by Arthur to lift his hips.

"You know," Arthur began, as casually as if he weren't changing a grown man out of a nappy, "I haven't had the chance to show you yet, but I bought something for your bed."

"Oh?"

"It's this absorbent pad, like they use in seniors' homes. It won't protect the sheets, but it'll keep anything from leaking down to your mattress, and make clean-up a hell of a lot easier. You can wash it with your clothes."

Merlin looked up at him briefly, but Arthur was much too focused on his task to meet his eyes. "And you couldn't have put it on before your stunt this morning?"

Arthur scoffed. "Of course not. The whole point was to surprise you. Besides, I cleaned that up myself, didn't I?"

"You did," Merlin conceded. "Is this your way of telling me you want to piss on me in bed more often?"

Arthur finally looked up at him then, patting his bum. "Definitely."

"You romantic, you."

Arthur laughed, discarding the soiled nappy and wipes into a spare bin bag. He stood, washing his hands and then helping Merlin up. "I'm going to find that jock you mentioned. It's with your briefs, right? You get into the shower; we're going to need to clean you out from the inside after that mess before you can graduate to your big boy pants."

Merlin nodded, stepping into the shower and turning the water to a lukewarm temperature. He turned under the spray a few times, lazily tugging at his cock, which fought to respond. He had hardly managed a twitch when Arthur returned, a bowl in one hand and an old, grey jock in the other. He set the jock on the edge of the sink, then rolled up his sleeves and switched the water to the lower spout, filling up the bowl.

"Lay back," he instructed, and Merlin followed his orders, planting his feet as firmly as he could and lifting his hips. Arthur's fingers played around his hole for a moment before he hooked one finger on his rim, pulling him open as best he could. Merlin lent his hands to the effort, stretching himself as far open as he was able.

The sensation of warm water filling him up was intense, and strangely pleasurable. Merlin had always enjoyed enemas, thought they rarely went through the effort of doing them. His toes curled slightly as Arthur refilled the bowl, pouring the water in until he could hold no more. Merlin shook his hips slightly from side to side, biting his lip at the feel of it all swishing around inside him. Arthur turned off the tap.

"Sit up, but don't get out yet." Merlin obeyed, practically purring with pleasure as it drained out of him, leaving behind a wonderfully hollow feeling. His cock had managed to fill some, rising slightly between his legs. He wanted to touch himself, but he returned to his previous position, holding himself open still for Arthur's inspection.

A finger rubbed at his rim, pulling slightly. Merlin gasped when he felt it joined by a warm tongue, first probing around the edge of his hole before dipping in. His cock twitched, needy and neglected, but he held still.

"Hm." Arthur sat back, looking contemplative. "Better, but you aren't quite clean yet. We can't have you putting anything on until you're clean enough to eat out, can we?"

Merlin shook his head, heart thumping in anticipation.

"Right. I'd better hose you out myself, then."

Arthur pulled off his shoes and socks, shucking the rest of his clothes as an afterthought, except his shirt. Merlin thought he looked ridiculous and incredibly handsome at once, his cock hanging down below the edge of his shirt, still soft.

He stepped into the tub, kneeling between his lover's feet. Merlin spread his legs father apart, keeping his fingers hooked inside himself and his hole stretched wide open.

Arthur ignored his arse for a moment, running a finger from the base of his cock to the tip.

"Look how big my boy has gotten," he murmured, feeling the vein on the underside of Merlin's prick. "Pretty soon his cock might be even bigger than his Daddy's."

Merlin's cock _was_ larger, but he bit his tongue, keeping that comment to himself. Arthur didn't like to be reminded... usually.

Arthur turned his attention back to Merlin's hole, lining up his own flaccid cock with it. He held just the tip in, not bothering to pull back his foreskin, and let loose, filling Merlin up with piss twice as quickly as he'd filled him with water.

Merlin couldn't hold back his groans of pleasure, nearly losing his grip on his hole. This was his favourite thing, absolutely; the only thing that could make it better would be getting fucked through the floor after, but he knew Arthur took longer to recover than he did, a consequence of being more than a decade older. 

Arthur drained himself quickly, rubbing the head of his cock all around Merlin's rim and balls once he was done. He sat back on his heels, admiring his work for a moment. To Merlin's confusion, he took off his shirt then, tossing it in the direction of his other clothes, and grabbed onto the back of Merlin's thighs before diving face-first into his arse, not hesitating to dip his tongue in and suck his own piss out of his lover's hole.

Merlin whined, sure that he was being corrected: _this_ had to be his favourite thing, enough to make him almost instantly hard and leaking. He kept his hands on his arse, holding himself open to Arthur's devious mouth, and still he could feel his cock soaking up the pleasure, painting his stomach with precome and bobbing with every slight movement he made.

Arthur nipped lightly at the edge of his hole, and he was done, shooting over his own stomach and chest. Arthur kept on at his arse, his tongue exploring inside him for all the piss he could reach. As Merlin started to whimper, sensitive and almost sore, he pulled him up into his lap by the shoulders, pushing his tongue into his mouth while Merlin let the last of Arthur's piss drip out of him.

He didn't usually enjoy the taste of piss, but he thought that on Arthur's tongue, accompanied by the heady taste of himself, he could grow to love it.

X

Regrettably, night came, in spite of their refusal to admit it. They had played for hours more, sharing fantasies they'd never told one another, kissing lazily, and enjoying a late meal in comfortable silence. Merlin stayed in his increasingly urine-soaked jock until after midnight; it had been christened as soon as he could push a decent amount of fluid from his bladder, and Arthur had "caught" him pissing in the sink by the toilet (it was easier, Merlin felt, than trying to drip through the fabric into the lower bowl, and he was sure big boys did not sit while pissing; besides, he had enjoyed watching his cloth-encased cock drain into the basin, seeing the yellow-tinted liquid spread around his cockhead and then trickle down), punishing him by making him sit on the toilet while Arthur showed him how a real man took a piss, soaking the thing thoroughly until Merlin's cock showed through it, clear as day.

He wouldn't wear it to bed, though, and so the jock was left in the sink, and both he and Arthur crawled into his bed, his lover spooning up behind him. They were naked and fighting to stay awake, but neither could muster an erection again; Arthur actually complained that he was sore, and though Merlin teased him, he, took, knew he wouldn't manage to get it up again without serious effort. They cuddled instead, Arthur kissing his shoulders and neck lazily, nuzzling behind his ear.

Merlin turned halfway in his arms, settling on his back. "I'm so tired, but I don't want to sleep."

"Neither do I," Arthur admitted. "I wish I could stay tomorrow as well."

Merlin didn't want to think about Arthur leaving. "And I have to piss, but I don't want to get out of bed."

"So don't. I told you I put that pad on the mattress."

He had, and Merlin had noticed how it made his bed feel just slightly off. "But I can't get it up again," he complained.

"So?"

Merlin yawned, stretching slightly. "Do you really want to sleep in piss just because I won't get up? Even with the pad, it'll still be a pain to clean in the morning, anyway."

Arthur pulled him closer, throwing a leg over Merlin's own. "I'll take care of it then. I don't care if we're wet, though. I don't want you to get up."

Merlin looked at him a moment. He could understand that; for all his arguing against it, he didn't want to leave Arthur's arms, either. "All right. Do you have to go?"

Arthur smirked, happy to have won. "Ladies first."

Merlin struggled slightly, trying to free his arms from Arthur's constrictor-like hold. "At least let me try and aim away from us."

"No."

Merlin sighed, rolling his hips slightly, trying to get his cock to point away from them — fruitlessly. He gave up when it fell to his thigh opposite Arthur, and concentrated, knowing that pissing the bed would be nearly as hard as pissing his diaper.

Arthur, seeing his trouble, lent him a hand, pressing his palm down over Merlin's bladder.

Merlin sighed happily as his bladder let go, hot piss splashing onto his thigh and trickling down to pool in the dip between his legs. It was sort of wonderful, getting to feel the relief and heat of it while still wrapped in Arthur's arms, lazy and content.

While he was still letting the last of it go, Arthur adjusted his own cock with one hand, laying it on Merlin's stomach. With considerably less effort than Merlin put into it, he started pissing, urine pooling up in Merlin's navel and then spilling out over his side, coating him in warmth where he had been cold, lacking Arthur's flesh pressed against him.

He knew it would feel cold and clammy in the morning, knew the sheets would stick to him and smell, possibly even stain, but Merlin couldn't bring himself to care.

Minutes later, with Arthur unable to fight off sleep any longer, he laid awake, wondering if he would have the pleasure of repeating that leisurely release in the morning, or if Arthur would just wake up, back to his other self, the one that honoured his wife and tolerated no nonsense in the office, the one that only kept a longing eye on Merlin instead of his hands and body.

Of course that would be it. For every meeting they'd had in the six years since they'd begun, since Merlin had still been in his mother's home and they'd had to sneak around to hotels and other secret places, Arthur had acted as though he could go to sleep as one man and wake up as another, like magic.

Merlin decided then that in the morning, he would make sure Arthur was the man who loved him by waking him up with a spray of piss and a long, wet kiss.

**Author's Note:**

> Further warning:  
> This story contains fantasies of public sex, brother/sister incest, parent/child incest, restraints, and dub-/non-con, all used as dirty talk and not actually realized. It's also worth noting that the watersports in this story is not really skippable, and that although Arthur and Merlin have a safeword, Merlin is sort of discouraged from using it, so some consent/communication issues could be read in certain parts.
> 
> If you've already read this, I do hope you enjoyed it!


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